Safety sear mechanism for blow back breech action



April 21, 1964 c. F. PACKARD ,637

SAFETY SEAR MECHANISM FOR BLOW BACK BREECH ACTION Filed Sept 1965 4 Sheets-Sheet 1 Fi g .1. 2O

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SAFETY SEAR MECHANISM FOR BLOW BACK BREECH-ACTION Filed Sept. 17, 1963 4 Sheets-Sheet 3 C. F. PACKARD SAFETY SEAR MECHANISM FOR BLOW BACK BREECH ACTION April 21, 1964 Filed Sept. 1'7, 1963 INVENTOR. E. hDT LESF F11 ck'nrd:

BY M April 21, 1964 c, F. PACKARD SAFETY SEAR MECHANISM FOR BLOW BACK BREECH ACTION Filed Sept. 17, 1963 4 Sheets-Sheet 4 INVENTOR. Ehnfles PPnn knri United States Patent SAFETY SEAR The invention described herein may be manufactured and used by or for the Government for governmental purposes without the payment to me of any royalty thereon.

This invention relates to automatic firearms which do not require locking of the bolt in battery position prior to the actuation of the firing pin by a pivotal hammer and is more particularly directed to means for interrupting the fall of the hammer in the event of any rebound by the bolt upon movement into battery position.

In many firearms designed to operate with relatively low-powered ammunition, the inertia of the bolt and the related recoiling parts may be safely utilized to delay the opening of the breech until the pressure in the firing chamber is reduced to the level at which the fired cartridge case can be readily extracted therefrom. This elimination of any positive mechanism for locking the breech at the instant of firing is commonly termed blowback operation and is particularly useful in. reducing the complexity and cost of firearm design.

Except for submachine guns, such as the US. cal. .45M3 which utilizes relatively massive bolts and are, therefore, restricted to relatively low rates of fire, firearms of the blowback type are generally of smaller caliber with bolts which are relatively light in weight. While the utilization of these lighter bolts provides the higher rates of fire required of modern military weapons, the tendency for such bolts to rebound out of battery position upon impact with the breech end of the barrel has heretofore restricted these blowback firearms to semiautomatic operation. In those firearms in which the firing pin is slidably carried in the bolt for actuation by the impact of a pivotal hammer, even a slight rebound of the bolt could result in the extremely dangerous possibility of firing the chambered cartridge while the breech is not completely closed. Furthermore, in the event the rebound of the bolt is of substantially greater extent, the corresponding reduction in the travel of the hammer could result in a failure to impart to the firing pin the energy required to detonate the primer in the chambered cartridge.

Accordingly, it is a broad object of this invention to provide full automatic fire capability for a small caliber firearm adapted for blowback operation and provided with a longitudinal firing pin slidably mounted in a bolt of relatively lightweight for actuation by a pivotal hammer.

It is a further object of this invention to provide a firearm of the aforesaid type having means for interrupting the fall of the hammer whenever the bolt is not completely in battery position.

Another object of this invention resides in providing a blowback firearm with an improved firing mechanism wherein the parts are simple and rugged in structure and operate in a safe and reliable manner despite irregular rebounding of the bolt during each firing cycle.

It is a specific object of the present invention to provide a firing mechanism as aforesaid wherein a sensing lever responsive to rebound of the bolt controls the fall of the hammer so that the chambered cartridge cannot be fired unless the bolt is at rest in full battery position.

The present invention essentially comprises the inclusion of a bolt sensing lever in an automatic firing mecha- 3,129,637 Patented Apr. 21, 1964 nism having a pivotal hammer for actuating a firing pin slidably mounted in a bolt adapted for blowback operation. The lever is pivotally mounted in position to be depressed by the bolt whenever the latter is not fully disposed in battery position. In this depressed position of the lever, a shoulder thereon engages a latch pivotally mounted to the free end of the hammer to retain the latter in the cocked position thereof. However, when the bolt is in proper battery position, the sensing lever is free to pivot upwardly into the recoil path of the bolt as the hammer spring urges the hammer toward impact with the firing pin. During this joint movement of the hammer and sensing lever, the hammer latch is moved out of engagement with the shoulder on the sensing lever to free the hammer for continuation of the firing movement thereof. As the hammer approaches firing position, a roller thereon cams the sensing lever downwardly out of the recoil path of the bolt and into position to again engage the hammer latch as the hammer is pivoted toward the cocked position thereof by the recoil movement of the bolt. Since the unrestricted movement of the bolt sensing lever occurs only if the bolt is fully in battery, it is readily apparent that any rebound of the bolt will in terrupt the fall of the hammer until such bolt returns to proper battery position.

Other objects and advantages of the invention will be apparent from the following specification and the accompanying drawings which are for the purpose of illustration only and in which:

FIG. 1 is a longitudinal section of the firearm with various parts shown in full in order to better illustrate the invention and the outer end of the hammer partially broken away in addition to show the manner in which the sensing lever latch is mounted therein;

FIG. 2 is a sectional view taken along lines 22 in FIG. 1 and enlarged to show the transverse configuration of the hammer and bolt sensing lever;

FIG. 3 is a fragmentary sectional view of the firing mechanism taken along line 3-3 in FIG. 2 with the forward end of the triggerpartially cut away and showing the position of the parts prior to the firing movement of the trigger;

FIG. 4 is a view similar to FIG. 3 but showing the parts immediately after release of the hammer by the trigger;

FIG. 5 is a view similar to FIG. 4 but showing the parts after release of the hammer from the sensing lever and with the upper end of the hammer partially broken away in the manner of FIG. 1;

FIG. 6 is a view similar to FIG. 5 but showing the hammer in the fully fired position thereof and the sensing lever pivoted out of the recoil path of the bolt;

FIG. 7 is a view similar to FIG. 6 but showing the position of the hammer and bolt sensing lever during the recoil movement of the bolt; and

FIG. 8 is a perspective view of the sensing lever.

As illustrated in the drawings, the firearm to which the present invention is particularly adapted is provided with a reciprocating bolt 12 having front and rear rib sections 14 on either side thereof in slidable engagement with mating grooves 16 formed along the inner wall surfaces of a receiver 18. Bolt 12 is adapted to be unlocked at the instant a chambered cartridge is fired but is held in battery position in contact with the breech face of the barrel 20 solely through the bias' of an operating spring 22 seated in a suitable hole 24 extending rearwardly into the stock 26. Spring 22 is retained in place by a slidable plug 28 in abutment with the rear end of an elongated rod 30 pivotally connected to the rear end of bolt 12.

A longitudinal firing pin 32 is slidably seated in bolt 12 and normally projects from the rear end thereof in response to the bias of a conventional coil spring (not shown). In addition, a suitable buffer 34 is mounted in the rear end of receiver 18 to receive the impact of bolt 12 at the conclusion of the recoil movement thereof. Buffer 34 is vertically slotted, as best shown at 35, for passage of rod 30 therethrough.

Firing pin 32 is actuated by a hammer 36 pivotally mounted at the forward end thereof on a transverse pin 38 fixedly secured in the walls of a trigger housing 39 which is in turn removably mounted in receiver 18 below the path of travel of bolt 12. The opposite and free end of hammer 36 is of increased width and includes a dished recess 40 in which a latch 42 is pivotally mounted, as shown at 44, for a purpose to be hereinafter explained. A torsion spring 46 is coiled about the opposite ends of a transverse pin 47 fixed in trigger housing 39' and is provided with a rectangular section 48 extending rearwardly into contact with the underside of hammer 36 for normally imparting counterclockwise rotation thereto toward impact with the rear end of firing pin 32. The free end of hammer 36 is also provided with an outwardly projecting lug 49 for engagement by a projecting nose 50 at one end of a sear 52 pivotally mounted on a pin 54 transversely fixed in trigger housing 39.

Counter-clockwise rotation is imparted to sear 52 by a suitable torsion spring 56 surrounding sear pin 54. The lower end of sear 52 is provided with a forwardly extending arm 58 disposed in the path of a ridge 59 extending transversely along the upper rear end of a trigger 60 pivotally mounted at the forward end thereof on hammer pin 38.

Trigger 60 is suitably slotted, as shown at 62, to bracket the front end of hammer 36 and is normally biased to the unpulled position thereof by a coil spring 64 seated in opposing recesses formed in an overhanging section 66 at the forward end of trigger 60 and in the floor of trigger housing 39. A safety plunger 70 rotatably mounted in trigger housing 39 serves to block pivotal movement of trigger 6i) and is slotted, as shown at 72, for rotation into an inactive position.

The above-described firing assembly is entirely adequate when the firearm is operated in semiautomatic fire. However, in the event fully automatic fire is desired, considerable difliculty would be encountered by the tendency for bolt 12 to rebound out of battery position during the interval in which hammer 36 is being urged forwardly into firing contact with firing pin 32. In many instances, the rebound could be of sufficient extent to reduce the impact of hammer 36 against firing pin 32 below the level required to detonate the primer in the chambered cartridge (not shown). Even if the rebound does not prevent firing of the chambered cartridge, it still may be enough to produce the extremely dangerous condition in which the breech is not completely closed at the instant of firing.

In accordance with the present invention, the firing mechanism includes a bolt sensing lever 74 pivotally mounted at the rear end thereof on a transverse pin 76 fixed in trigger housing 39. Pivot pin 76 is located above sear 52 but below the recoil path of bolt 12 to permit lever 74 to pivot between a longitudinal position parallel with the underside of bolt 12 and a tilted position in which the front end of lever 74 is lifted behind a forwardly sloped wall 78 at the rear end of bolt 12 formed by removing a portion thereof as indicated at 80. The length of lever 74 is such that the tilted position thereof is permitted only when bolt 12 is completely in battery position as best shown in FIGS. 4 and 5. In order to ensure that the upward pivotal movement of lever 74 is initiated as bolt 12 is moving into battery position, the forward end of lever 74 is rearwardly beveled as indicated at 82.

As best shown in FIG. 4, the back side of lever 74 is cut away to form a recess 83 provided with a vertical rear wall 34 terminated by a transverse shoulder 86 and an upwardly and forwardly inclined cam surface 88 in the forward wall thereof. Latch 42 on hammer 36 is formed with a substantially rectangular arm 90 which engages with transverse shoulder 86 to impart the upward pivotal movement of hammer 36 to lever 74. A coil spring 92 seated in dished recess 40 of hammer 36 bears against arm to urge latch 42 in a clockwise direction for engagement with shoulder 86 on lever 74.

In automatic operation of the firearm, trigger 6!) is pulled to pivot sear 52 out of engagement with hammer 36 which thereupon pivots toward firing contact with firing pin 32 in response to the bias of spring 46. This pivotal movement of hammer 36 is imparted to lever 74 through the engagement between latch 42 and shoulder 86. Thus, the forward end of lever 74 is lifted into cutaway portion 86 of bolt 12 to lie in the recoil path thereof as shown in FIG. 4. However, since hammer 36 and lever 74 pivot in opposite directions, latch 42 will disengage form shoulder $6 to free lever 74 for return to the longitudinal position thereof. Such disengagement is accelerated by vertical wall 84 which forces latch 42 into hammer recess 4@ against the bias of spring 92. In order to facilitate the return of lever 74 to the longitudinal position thereof, hammer 36 is provided with an outwardly projecting roller 94 in position to engage with cam surface 83 on lever 74 as best shown in FIG. 5. By the time hammer 36 strikes firing pin 32, roller 94 will have cammed lever 74 out of the recoil path of bolt 12 into abutment with a suitable stop 96 fixed in receiver 13 as shown in FIG. 6.

Upon the firing of a chambered cartridge (not shown), bolt 12 is momentarily retained in battery position by the inertia thereof and the resistance to compression of operating spring 22. While of extremely short duration, such delay permits a reduction in chamber pressure of sufiicient extent to enable extraction of the fired cartridge case without interrupting the recoil movement of bolt 12. During this rearward movement of bolt 12, hammer 36 is pivoted downwardly thereby, as best shown in FIG. 7, until latch 42 moves past the corner of shoulder 86 on lever 74 to engage therewith and retain hammer 36 in a cocked position while bolt 12 returns to the battery position thereof.

As bolt 12 approaches battery position and the lower corner of sloped wall '78 passes the point of origination of bevel 82 on the front end of lever 74, the latter will begin the pivot upwardly into the recoil path of bolt 12 before any rebound thereof out of battery position. However, before lever 74 can pivot sufficiently to disengage from latch 42, the rebound produced by the impact between the front face of bolt 12 and the breech face of barrel 2% will cause the former to press against the front end of lever 74 with suificient force to stop further pivotal movement thereof. Thus, the firing release of hammer 36 will be delayed while bolt 12 is under the influence of rebound forces. In some instances, the original rebound force of bolt 12 may be of sufficient intensity to provide several consecutive delays in the pivotal movement of lever 74.

Once the rebound of bolt 12 is completely dissipated, the continued pivotal movement of lever 74 will free hammer 3%) for impact with firing pin 32. During the fall of hammer 36, roller 94 thereon will cam lever 74 downwardly to the longitudinal position shown in FIG. 6 which will permit unobstructed recoil of bolt 12 upon discharge of firing pin 32 by hammer 36. As bolt 12 recoils, hammer 36 is pivoted downwardly thereby, as best shown in FIG. 7, until latch 42 engages with shoulder 86 on lever 74 to hold hammer 36 in the cocked position thereof. The foregoing cycle of operation will be repeated as long as cartridges are fed into the firearm and trigger 60 is held to the rear. However, once trigger 60 is released, sear 52 will engage hammer lug 49 and prevent further firing release of hammer 36.

It frequently becomes necessary to retract bolt 12 manually as, for example, whenever the condition of the breech or firing chamber must be inspected. Since a portion of bevel 82 extends upwardly into the recoil path of bolt 12 whenever firing has terminated, the slight downward movement imparted thereby to lever 74 is correspondmgly transmitted by latch 42 to hammer 36. Although this movement of hammer 36 is extremely small, it still is sufficient to disengage lug 49 from sear nose 50. In the event of any accidental pivoting of trigger 6th at this time, hammer 36 would be freed to strike firing pin 32 as bolt 12 reaches battery were it not for the existence of latch 42 which serves as a secondary sear to hold hammer 36 in the cocked position. Accordingly, unlike ordinary firearms of this type wherein the firing mechanism does not include any safety or secondary sear, lever 74 of the present invention positively bars any accidental firing during manual retraction of bolt 12.

Thus, there is here provided a firing mechanism which is uniquely suited for firearms with blowback bolts of the type which tend to bounce out of battery position. Any inadequate or premature release of the hammer is simply and positively prevented by pivotal lever 74 which delays the fall of hammer 36 whenever bolt 12 is not at rest in battery position. Such structure permits the utilization of a relatively lightweight blowback bolt in an automatic firearm without the failures to fire which otherwise would be encountered as a result of the tendency for such bolt to bounce out of battery position at the conclusion of counterrecoil movement.

Although a particular embodiment of the invention has been described in detail herein, it is evident that many variations may be devised within the spirit and scope thereof and the following claims are intended to include such variations.

I claim:

1. In a firearm having a reciprocal bolt adapted to be unlocked in battery position, a firing pin slidably mounted in the bolt, and a spring-biased hammer mounted for pivotal movement between a fired position in contact with the firing pin and a cocked position imparted thereto by the recoil movement of the bolt, the improvement of a lever pivotally mounted at one end thereof in position to retain the hammer in the cocked position until the bolt reaches battery position and frees the opposite end of said lever for movement into the recoil path of the bolt and out of cocking engagement with the hammer, and means on the hammer for camming said lever out of the recoil path of the bolt during the firing movement of the hammer.

2. In a firearm having a reciprocal bolt adapted to be unlocked in battery position, the combination of a longitudinal firing pin slidably mounted in the bolt, a hammer pivotally mounted at the forward end thereof for movement between a fired position in contact with the rear end of said firing pin and a cocked position imparted thereto by the recoil movement of the bolt, a lever pivotally mounted at the rear end thereof to lie beneath the bolt and retain said hammer in the cocked position thereof until the bolt reaches battery position, spring means normally urging said hammer to the fired position thereof and thereby simultaneously urging said lever to pivot the front end thereof into the recoil path of the bolt at the conclusion of battery movement to free said hammer from the cocked position thereof, and means on said hammer for camming said lever out of the recoil path of the bolt during movement of said hammer to the fired position thereof.

3- In all a omatic firearm having a longitudinally slidable bolt adapted for reciprocal movement into and out of unlocked battery position, a longitudinal firing pin slidably mounted in the bolt, a hammer pivotally mounted at the forward end thereof below the bolt, a spring normally urging said hammer toward firing impact with the rear end of said firing pin, a primary sear for retaining said hammer in a cocked position, trigger means for effecting the release of said primary sear, a lever pivotally mounted at the rear end thereof at a point below the recoil path of the bolt and rearwardly of the cocking engagement between said hammer and said sear, said lever being of suificient length to be depressed by the underside of the bolt until the conclusion of battery movement thereof, a shoulder on said lever for blocking the firing movement of said hammer until the front end of said lever is free to pivot upwardly into the recoil path of the bolt in response to the pivotal movement imparted to said hammer by said hammer spring, and a roller on said hammer for camming said lever downwardly out of the recoil path of the bolt during movement of said hammer into impact with said firing pin.

4. The combination defined in claim 3 including latch means pivotally mounted in the rear end of said hammer to engage with said blocking shoulder on said lever and serve as a secondary sear for retaining said hammer in the cocked position thereof during automatic fire.

5. In a firearm having a reciprocal bolt adapted to be unlocked in battery position, the combination of a longitudinal firing pin slidably mounted in the bolt, a hammer pivotally mounted at the forward end thereof for movement between a fired position in contact with the rear end of said firing pin and a cocked position below the recoil path of the bolt and substantially parallel thereto, a lever pivotally mounted at the rear end thereof rearwardly of said hammer for movement between a position below and substantially parallel to the recoil path of the bolt and an elevated position in the recoil path of the bolt for blocking rebound thereof out of battery position, a shoulder projecting from the side of said lever, a latch pivotally mounted in the rear end of said hammer, a spring seated between said hammer and said latch to urge the latter into engagement with said shoulder on said lever for blocking firing movement of said hammer, said lever being of sufficient length to contact the underside of the bolt and retain said lever in position to block firing movement of said hammer until the bolt reaches battery position and permits said lever to pivot into the recoil path of the bolt and out of engagement with said latch on said hammer, and means for camming said lever downwardly out of the recoil path of the bolt during firing movement of said hammer.

6. The combination defined in claim 5 wherein said last-mentioned means comprises a forwardly and upwardly sloped cam surface on the side of said lever and a roller on the side of said hammer engageable with said cam surface on said lever for pivoting the latter out of the recoil path of the bolt prior to impact between said hammer and said firing pin.

7. The combination defined in claim 6 wherein the front end of said lever is rearwardly beveled to permit the upward pivotal movement imparted thereto by said hammer to be initiated while the bolt is still moving into battery position.

No references cited, 

1. IN A FIREARM HAVING A RECIPROCAL BOLT ADAPTED TO BE UNLOCKED IN BATTERY POSITION, A FIRING PIN SLIDABLY MOUNTED IN THE BOLT, AND A SPRING-BIASED HAMMER MOUNTED FOR PIVOTAL MOVEMENT BETWEEN A FIRED POSITION IN CONTACT WITH THE FIRING PIN AND A COCKED POSITION IMPARTED THERETO BY THE RECOIL MOVEMENT OF THE BOLT, THE IMPROVEMENT OF A LEVER PIVOTALLY MOUNTED AT ONE END THEREOF IN POSITION TO RETAIN THE HAMMER IN THE COCKED POSITION UNTIL THE BOLT REACHES BATTERY POSITION AND FREES THE OPPOSITE END OF SAID LEVER FOR MOVEMENT INTO THE RECOIL PATH OF THE BOLT AND OUT OF COCKING ENGAGEMENT WITH THE HAMMER, AND MEANS ON THE HAMMER FOR CAMMING SAID LEVER OUT OF THE RECOIL PATH OF THE BOLT DURING THE FIRING MOVEMENT OF THE HAMMER. 